Polymeric implants are useful as delivery systems and/or as mechanical barriers. Implants such as preformed membranes or films have been described. However, many of these implants have limited properties and produce inferior results either as mechanical barriers or delivery systems.
Several implant techniques have been used in medical and dental applications. One application of interest is the use of implants in treatment of periodontal disease. Surgery alone does not result in restoration of lost periodontium. Successful periodontal restoration is known to occur if periodontal ligament cells are allowed to colonize root surfaces preferentially over gingival epithelial cells, gingival fibroblasts or osteoblasts. Microporous membranes, such as the Millipore.RTM. filter and GORE-TEX.RTM. membranes, have been used for periodontal tissue regeneration. Typically, the periodontal flap is cut, and the membrane is surgically inserted to cover the surface of the tooth root and to physically occlude epithelial cells from apically migrating along the root surface.
Those membranes, however, have several drawbacks. Besides variable results, a second surgical entry is needed to remove the membrane after tissue regeneration has been achieved because the membranes are not biodegradable. There is also a higher incidence of infection in connection with their use.
To preclude surgical removal of the implant, membranes made of bioabsorbable material, such as microfibrillar collagen, polylactic acid, and polygalactin (Vicryl.RTM.) mesh have been used. Results have been variable, and the therapeutic effect of these membranes has been unpredictable. In addition, fitting and positioning these membranes to the implant site is time-consuming and cumbersome. The degradation time of membranes composed of collagen has been variable, and the risk of adverse immunological reaction to this foreign protein material in the body presents a major concern.
Therefore, an object of the invention is to provide a composition comprising a biodegradable or bioerodible polymer for use as an implant in an animal including a human. Another object is the development of an implant that will eliminate the need for its surgical removal after its purpose has been achieved. Another object is to provide a composition which may be administered to an implant site in liquid form and which is capable of solidifying in situ to form an implant. A further object of the invention is to provide a biodegradable implant which may be used to enhance connective cell or tissue growth and deter growth of epithelial cells and tissue into the core of the implant. Yet another object is to provide an implant which is capable of delivery of a drug or other medicament over a desired period of time. A further object is to provide an implant for providing controlled release delivery of at least one biologically-active agent for stimulation and/or enhancement of physiological or biological activity in an animal.